Method for manufacturing sealing device, and sealing device

ABSTRACT

A method for manufacturing a sealing device to improve the positioning accuracy of a parting operation while also improving manufacturing efficiency. The method includes molding an elastomeric cylindrical molded body ( 100   a ) with a plurality of cylindrical surface portions ( 130 ) and a plurality of annular outer peripheral convex portions ( 110 ) arranged alternately on an outer peripheral side thereof, and further provided with a plurality of cylindrical surface portions and a plurality of annular inner peripheral convex portions arranged alternately on an inner peripheral side thereof. The cylindrical surface portions on the outer peripheral side and the cylindrical surface portions on the inner peripheral side, as well as the outer peripheral convex portions and the inner peripheral convex portions are provided so as to be at the same positions in the axial direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/438,708, filed Apr. 27, 2015, which is a National Stage ofInternational Application No. PCT/JP2013/052252, filed Jan. 31, 2013(now WO 2014/068999A1), which claims priority to Japanese ApplicationNo. 2012-238900, filed Oct. 30, 2012. The entire disclosures of each ofthe above applications are incorporated herein by reference.

FIELD

The present disclosure relates to a method for manufacturing a sealingdevice that seals an annular gap between two members configured to bereciprocally movable relative to each other, and relates to a sealingdevice itself.

BACKGROUND

Conventionally, there has been known an elastomeric sealing device thatseals an annular gap between two members configured to be reciprocallymovable relative to each other. Such a sealing device is used in such amanner that it is fitted in an annular fitting groove formed on one ofthe two members so that it slides on the other member. As examples ofsuch a sealing device, a so-called D ring having a D-shaped crosssection and a rectangular ring having a rectangular cross section withan annular convex portion formed on its sliding side are known (refer toa first patent literature).

In such sealing devices, especially in cases where a sealing device hasa large inside diameter, in terms of cost or manufacturing efficiency,it is advantageous to manufacture individual sealing devices byconducting a parting operation to one molded body, rather than moldingindividual sealing devices separately.

However, in the case of a sealing device in which an annular convexportion is formed on an inner peripheral side thereof, when theabove-mentioned parting operation is to be conducted, it is difficult torecognize the position of the annular convex portion. Therefore, thereis a problem that it is difficult to achieve a high positioning accuracyof the parting operation (refer to a second patent literature).

In addition, in the case of a sealing device such as a D ring mentionedabove, there is also a disadvantage that its sliding resistance tends tobecome high because the main body portion of the sealing device isconstrained in the fitting groove and thereby making it difficult forthe ring to deform.

CITATION LIST Patent Literature

-   First Patent Literature: Japanese patent application laid-open No.    H9-222169 Second Patent Literature: Japanese patent No. 2794568

SUMMARY Technical Problem

The object of the present disclosure is to provide a method formanufacturing a sealing device which makes it possible to improve thepositioning accuracy of a parting operation while also improvingmanufacturing efficiency, even if the sealing device has an annularinner peripheral convex portion on its inner peripheral side, and tofurther provide a sealing device that is capable of achieving a bettersliding property and suppressing a breakage thereof.

Solution to Problem

In order to solve the above-mentioned problems, the present disclosureadopts the following means.

That is, a method for manufacturing a sealing device, the sealing deviceis an elastomeric sealing device that is fitted in an annular fittinggroove formed on one of two members so as to seal an annular gap betweenthe two members, the two members configured to be reciprocally movablerelative to each other, characterized by including: conducting a processfor molding an elastomeric cylindrical molded body that is provided witha plurality of cylindrical surface portions and a plurality of annularouter peripheral convex portions arranged alternately on an outerperipheral side thereof, and further provided with a plurality ofcylindrical surface portions and a plurality of annular inner peripheralconvex portions arranged alternately on an inner peripheral sidethereof, wherein the cylindrical surface portions on the outerperipheral side and the cylindrical surface portions on the innerperipheral side are provided so as to be at the same positions in anaxial direction, and the outer peripheral convex portions and the innerperipheral convex portions are also provided so as to be at the samepositions in the axial direction; and conducting a process forconducting a parting operation to the molded body along the individualcylindrical surface portions on the outer peripheral side.

According to the present disclosure, a plurality of sealing devices canbe obtained from one molded body by conducting the parting operation tothe cylindrical molded body. Accordingly, the manufacturing efficiencycan be improved when compared with the case where individual sealingdevices are molded separately. In addition, upon conducting, the partingoperation can be conducted along the individual cylindrical surfaceportions on the outer peripheral side, so that the positioning thereofbecomes easy, and hence the positional accuracy of the parting operationcan be improved. Therefore, even in the case of the sealing device whichrequires the annular inner peripheral convex portions on the innerperipheral side thereof, it is possible to improve the positioningaccuracy of the parting operation.

In addition, a sealing device according to the present disclosure is asealing device, that is an elastomeric sealing device and is fitted inan annular fitting groove formed on one of two members configured to bereciprocally movable relative to each other, so as to seal an annulargap between these two members, characterized in that: on an outerperipheral side thereof, an annular outer peripheral convex portion; andcylindrical surface portions provided on both sides of the outerperipheral convex portion are formed; and on an inner peripheral sidethereof, an annular inner peripheral convex portion; and cylindricalsurface portions provided on both sides of the inner peripheral convexportion are formed.

According to the present disclosure, since the annular convex portionsare formed on both the outer peripheral side and the inner peripheralside, the sealing device can be applied to both outer peripheral sidesliding usage and inner peripheral side sliding usage. In addition, dueto the fact that a reaction force against the compression of the sealingdevice in a radial direction can be suppressed, in combination with thefact that the sealing device can be easily deformed within the fittinggroove, it is possible to reduce the sliding resistance of the sealingdevice in a synergetic manner.

Advantageous Effects of Disclosure

As described above, according to the method for manufacturing a sealingdevice according to the present disclosure, it is possible to improvethe positioning accuracy of a parting operation while also improving themanufacturing efficiency, even if the sealing device has an annularinner peripheral convex portion on its inner peripheral side. Inaddition, according to the sealing device of the present disclosure, abetter sliding property can be achieved and a breakage thereof can besuppressed.

DRAWINGS

FIG. 1 is a side view of a sealing device according to a first exampleof the present disclosure.

FIG. 2 is a plan view of the sealing device according to the firstexample of the present disclosure.

FIG. 3 is a cross sectional view of the sealing device according to thefirst example of the present disclosure.

FIG. 4 is a schematic cross sectional view showing a fitted state of thesealing device according to the first example of the present disclosurewhen fitted in a fitting groove.

FIG. 5 is a schematic cross sectional view showing usage state of thesealing device according to the first example of the present disclosure.

FIG. 6 is a schematic cross sectional view showing a fitted state of thesealing device according to the first example of the present disclosurewhen fitted in a fitting groove.

FIG. 7 is an explanatory view explaining a molding process of thesealing device according to the first example of the present disclosure.

FIG. 8 is a schematic cross sectional view of a mold used in the moldingprocess according to the first example of the present disclosure.

FIG. 9 is a partially broken cross sectional view of a molded bodyobtained in the molding process according to the first example of thepresent disclosure.

FIG. 10 is an explanatory view explaining a parting operation processaccording to the first example of the present disclosure.

FIG. 11 is a schematic cross sectional view showing a fitted state of asealing device according to a second example of the present disclosurewhen fitted in a fitting groove.

FIG. 12 is a schematic cross sectional view showing a fitted state of asealing device according to a third example of the present disclosurewhen fitted in a fitting groove.

FIG. 13 is a schematic cross sectional view showing a fitted state of asealing device according to a fourth example of the present disclosurewhen fitted in a fitting groove.

FIG. 14 is a schematic cross sectional view showing a fitted state of asealing device according to a fifth example of the present disclosurewhen fitted in a fitting groove.

DETAILED DESCRIPTION

Hereinafter, modes for carrying out the present disclosure will beexemplarily described in detail based on examples thereof with referenceto the drawings. However, the dimensions, materials, shapes, relativearrangements and so on of constituent parts described in the examplesare not intended to limit the scope of the present disclosure to thesealone in particular unless specifically described.

First Example

With reference to FIGS. 1 to 10, a sealing device and a method formanufacturing the sealing device according to a first example of thepresent disclosure will be described. Note that the sealing deviceaccording to the present example can be preferably used as a hydraulicseal for reciprocating motions in a transmission system such as an AT(automatic transmission), a CVT (continuously variable transmission) orthe like in automobiles. In addition, it can also be used as a seal forreciprocating motions in other general industrial machinery such asconstruction machinery, agricultural machinery, and so on.

<Sealing Device>

With reference to FIGS. 1 to 3, a sealing device according to the firstexample of the present disclosure will be described. FIG. 1 is a sideelevation view of the sealing device according to the first example ofthe present disclosure. FIG. 2 is a plan view of the sealing deviceaccording to the first example of the present disclosure. FIG. 3 is across sectional view (A-A cross sectional view in FIG. 2) of the sealingdevice according to the first example of the present disclosure.

The sealing device 100 according to the present example is anelastomeric annular member. On an outer peripheral side of the sealingdevice 100, an annular outer peripheral convex portion 110, andcylindrical surface portions 111, 112 provided on both sides of theouter peripheral convex portion 110 are formed. Moreover, on an innerperipheral side of the sealing device 100, an annular inner peripheralconvex portion 120 and cylindrical surface portions 121, 122 provided onboth sides of the inner peripheral convex portion 120 are formed.

Here, in the present example, the shapes and dimensions of the crosssections of the outer peripheral convex portion 110 and the innerperipheral convex portion 120 are designed to be the same (refer to FIG.3). Also, in the present example, the cross sectional shapes at the tipsof the outer peripheral convex portion 110 and the inner peripheralconvex portion 120 are circular arcs. In addition, the cylindricalsurface portions 111, 112 on the outer peripheral side and thecylindrical surface portions 121, 122 on the inner peripheral side aredesigned so as to be at the same positions, respectively, in an axialdirection. Moreover, the outer peripheral convex portion 110 and theinner peripheral convex portion 120 are also designed so as to be at thesame positions, respectively, in the axial direction. Accordingly, thecross sectional shape of the sealing device 100 is of a symmetricalconfiguration with respect to a centerline in a radial direction. Notethat, as will be described later, due to its demolding property duringmolding, it is necessary to set the projection height of one of theouter peripheral convex portion 110 and the inner peripheral convexportion 120 to be relatively low, and hence, the projection heights ofthe outer peripheral convex portion 110 and the inner peripheral convexportion 120 in the present example are set lower in comparison with thecases of other examples to be described later. More specifically, theprojection heights of the outer peripheral convex portion 110 and theinner peripheral convex portion 120 (projection heights from thecylindrical surface portions) are set within a range from 0.2 mm to 0.4mm, inclusive. Thus, the demolding resistance can be reduced.

<Sealing Structure and Behavior of the Sealing Device>

With reference especially to FIGS. 4 and 5, a sealing structureemploying the sealing device 100 according to the present example andthe behavior of the sealing device 100 will be described.

The sealing device according to the present disclosure is fitted in anannular fitting groove formed in one of two members configured to bereciprocally movable relative to each other, so as to seal an annulargap between these two members. In the following, as an example thereof,among a shaft 200 and a housing 300 that are configured to bereciprocally movable relative to each other, there is shown the case ofthe sealing device 100 which is used so as to be fitted in an annularfitting groove 210 formed on the shaft 200. FIG. 4 is a schematic crosssectional view showing a state where the sealing device 100 according tothe present example of the present disclosure is fitted in the annulargroove 210, and FIG. 5 is a schematic cross sectional view showing usagestate of the sealing device 100 according to the present example of thepresent disclosure.

As mentioned above, in the case of the sealing device 100 according tothe present example, the projection height of the outer peripheralconvex portion 110 is set to be relatively low. For this reason, thecylindrical surface portions 111, 112 on the outer peripheral side ofthe sealing device 100 are set so as to protrude from the fitting groove210 so that the outer peripheral convex portion 110 can slide on aninner peripheral surface of a shaft hole 310 in the housing 300 in amore reliable manner. That is, as shown in FIG. 4, in a state where thesealing device 100 is fitted in the fitting groove 210, a distance “a”from a groove bottom surface to the cylindrical surface portions 111,112 is set to be longer than a depth “b” of the fitting groove 210. Inaddition, in order to prevent edge portions of the ends of thecylindrical surface portions 111, 112 from being bitten into a minuteannular gap S outside the fitting groove 210 and between the shaft 200and the housing 300, due to the fact that the cylindrical surfaceportions 111, 112 are set to protrude from the fitting groove 210,relatively large chamfers 211 are formed between each of the sidesurfaces of the fitting groove 210 and the surface of the shaft 200.

When the shaft 200 and the housing 300 reciprocally move relative toeach other, the outer peripheral convex portion 110 on the sealingdevice 100 deforms when being dragged by the inner peripheral surface ofthe shaft hole 310 of the housing 300. In addition, in the case of thesealing device 100 according to the present example, because the innerperipheral convex portion 120 is also formed on a groove bottom side ofthe fitting groove 210, spaces are formed between the cylindricalsurface portions 121, 122 on the both sides of the inner peripheralconvex portion 120 and the groove bottom of the fitting groove 210,respectively. Accordingly, the constraining force is reduced by theextent of the proportion of the above-mentioned spaces, so that when theshaft 200 and the housing 300 reciprocally move relative to each other,the sealing device 100 also deforms within the fitting groove 210.

Note that in FIG. 5, there is shown a state where the housing 300 ismoving relatively to the right side in the drawing with respect to theshaft 200. In this state, the sealing device 100 deforms so as to bedragged to the right side in the drawing by the inner peripheral surfaceof the shaft hole 310, while deforming within the fitting groove 210, aswell.

<Advantages of the Sealing Device According to the Present Example>

According to the sealing device 100 of the present example, the annularconvex portions (the outer peripheral convex portion 110 and the innerperipheral convex portion 120) are formed on both the outer peripheralside and the inner peripheral side. Accordingly, the sealing device 100can be applied to both outer peripheral side sliding usage and innerperipheral side sliding usage. In other words, as mentioned above, thesealing device can be used not only for usage in which it is fitted inthe fitting groove 210 of the shaft 200 so as to allow the outerperipheral convex portion 110 to slide on the inner peripheral surfaceof the shaft hole in the housing 300, but also for usage in which it isfitted in an annular fitting groove formed on the inner periphery of theshaft hole of the housing so as to allow the inner peripheral convexportion 120 to slide on to the outer peripheral surface of the shaft.

A brief description will be given to a case in which the sealing device100 is used for such usage, while referring to FIG. 6. In an exampleshown in FIG. 6, the sealing device 100 configured as mentioned above isfitted into an annular fitting groove 310 formed on a housing 300, amonga shaft (not shown) and the housing 300 that are configured to bereciprocally movable relative to each other. Note that in thisillustrated example, too, in a state where the sealing device 100 isfitted in the fitting groove 310, a distance “a” from a groove bottomsurface to the cylindrical surface portions 121, 122 is set to be longerthan a depth “b” of the fitting groove 310. It goes without saying thatin this illustrated example, too, the same operational effects can beobtained as those in the case where it is used for the above-mentionedusage shown in FIGS. 4 and 5.

In addition, since the annular convex portions (the outer peripheralconvex portion 110 and the inner peripheral convex portion 120) areformed on both the outer peripheral side and the inner peripheral side,it is possible to suppress a reaction force against the compression in aradial direction. Moreover, as mentioned above, the constraining forceis reduced by the extent of the proportion of the spaces between thecylindrical surface portions 121, 122 on the both sides of the innerperipheral convex portion 120, and the groove bottom of the fittinggroove 210, whereby the sealing device 100 can easily deform within thefitting groove 210. In other words, the followability of the sealingdevice 100 becomes high. With these advantages combined, the slidingresistance can be reduced in a synergetic manner. Accordingly, slidingwear of the sealing device 100 can be suppressed, thereby making itpossible to enhance the durability thereof. For example, in cases wherethe sealing device 100 is used as a hydraulic seal for reciprocatingmotions in a CVT, even under the condition that strokes of minute widthsare generated by a CVT pulley or the like, formation of an oil film on asliding portion is done in a more reliable manner so that the slidingresistance can be thereby reduced. Note that it goes without saying thateven in cases where the sealing device 100 is used for inner peripheralside sliding usage, similar mechanism will apply, and thus it ispossible to obtain the similar operational effect.

Moreover, since the cylindrical surface portions 111, 112 are formed onthe both sides of the outer peripheral convex portion 110, it ispossible to suppress the annular outer peripheral convex portion 110from protruding into a minute annular gap S in the outside of thefitting groove 210. Note that it goes without saying that even in caseswhere the sealing device 100 is used for inner peripheral side slidingusage, similar mechanism will apply, and thus it is possible to obtainthe similar operational effects.

Further, in the case of the sealing device 100 according to the presentexample, the shapes and dimensions of the cross sections of the outerperipheral convex portion 110 and the inner peripheral convex portion120 are designed to be the same, and the cross sectional shapes thereofare of a symmetrical configuration with respect to their centerline in aradial direction. Accordingly, even if the sealing device is used withtwo sides thereof are turned around, a function equivalent to that inthe case where it is used in a normal manner can be obtained.

Note that in the case of the sealing device 100 according to the presentexample, the projection height of the inner peripheral convex portion120 is set to be relatively high, as compared with other examples to bedescribed later. For this reason, when compared with the cases of theother examples, the amount of deformation of the sealing device 100within the fitting groove 210 can be made large, and hence, thefollowability thereof can be increased.

<Method for Manufacturing the Sealing Device>

With reference to FIGS. 7 to 10, a method for manufacturing the sealingdevice 100 according to the present example of the present disclosurewill be described. In the manufacturing method according to the presentexample, individual sealing devices are not molded separately, butinstead a plurality of sealing devices are obtained from one molded bodyby first molding the molded body and then conducting the partingoperation to this molded body. In the following, a molding process and aparting operation process will be described.

«Molding Process»

With reference to FIGS. 7 to 9, the molding process will be described.FIG. 7 is an explanatory view explaining the molding process of thesealing device according to the first example of the present disclosure,and FIG. 8 is a schematic cross sectional view of a mold used in themolding process according to the first example of the presentdisclosure. Note that in FIG. 7, the whole of a molding device isillustrated cross-sectionally (a vertically intersected cross section),and in FIG. 8, a horizontal cross section of the mold is illustrated. Inaddition, FIG. 9 is a partially broken cross sectional view of a moldedbody obtained by the molding process according to the first example ofthe present disclosure.

In the present example, a molded body 100 a is formed by injectionmolding. As the injection molding is a well-known technique, a detailedexplanation thereof is omitted. Note that in the present example, themolded body 100 a is formed by a screw type injection molding machine500. This screw type injection molding machine 500 is roughly composedof an injection mechanism 510 which injects a material 150 while keepingit in a molten state, and a molding mechanism 520 which molds the rubbermaterial in the molten state injected into the interior of a cavity Cfrom the injection mechanism 510. The molding mechanism 520 is providedwith an inner mold 521 of a substantially columnar shape, an outer mold522 of a substantially cylindrical shape, and a lower mold 523 which isdisposed at a lower side of these molds.

When molding is conducted, the molten material is injected into theinterior of the cavity C by the injection mechanism 510 after clampingof the molds is completed. Then, after the material has solidified andthe molds have been cooled, the inner mold 521 is moved in a lowerdirection in the drawing together with the lower mold 523. At this time,there may be a case where the molded body 100 a is held in the inside ofthe outer mold 522 or a case where the molded body 100 a is held on theoutside of the inner mold 521 so that it moves together with the innermold 521 in the lower direction in the drawing. In other words, whetherit will be held in the outer mold 522 or on the inner mold 521 isdetermined according to the relation between the projection height ofthe outer peripheral convex portion 110 and the projection height of theinner peripheral convex portion 120 in the sealing device 100. In thecase of the present example, both of the projection heights are set tobe the same, and hence they are held in the outer mold 522, but in theexamples to be described later, in cases where the projection height ofthe inner peripheral convex portion is set to be about several timeshigher than the projection height of the outer peripheral convexportion, the molded body 100 a is held on the outside of the inner mold521 so that it moves in the lower direction in the drawing together withthe inner mold 521.

Then, in the case of the present example, after the inner mold 521 hasbeen moved in the lower direction in the drawing together with the lowermold 523, the molded body 100 a in a state of being held inside theouter mold 522, is taken out. Note that it goes without saying that inan example to be described later, in cases where the molded body 100 ais held on the inner mold 521, the molded body 100 a is removed from theinner mold 521.

The elastomeric cylindrical molded body 100 a obtained by the abovemolding process includes a plurality of cylindrical surface portions 130and a plurality of annular outer peripheral convex portions 110 arrangedalternately on its outer peripheral side and includes a plurality ofcylindrical surface portions 140 and a plurality of annular innerperipheral convex portions 120 arranged alternately on its innerperipheral side. In addition, the cylindrical surface portions 130 onthe outer peripheral side and the cylindrical surface portions 140 onthe inner peripheral side are provided so as to be at the same positionsin an axial direction. Moreover, the outer peripheral convex portions110 and the inner peripheral convex portions 120 are also provided so asto be at the same positions in the axial direction. Note that in orderto carry out the parting operation as described below, the widths in theaxial direction of the cylindrical surface portions 130, 140 are eachset to be equal to or more than 0.2 mm.

«Parting Operation Process»

With reference to FIG. 10, the parting operation process will beexplained. FIG. 10 is an explanatory view explaining the partingoperation process according to the first example of the presentdisclosure.

The sealing device 100 can be obtained by cutting the molded body 100 aobtained from the above-mentioned molding process with a use of aparting tool 620, while the molded body 100 a is in a state where it ismounted on a rotating mechanism 610 and is being rotated by the rotatingmechanism 610. Then, by pressing a tip of the parting tool 620 onto acenter position of the cylindrical surface portions 130 in the axialdirection on the outer peripheral side of the molded body 100 a (see aportion indicated by a broken line in FIG. 10), parting operation isdone along this position. By conducting such parting operation to allthe cylindrical surface portions 130 one after another, a plurality ofsealing devices 100 can be obtained from the one molded body 100 a.

Note that in order to improve the quality of each sealing device 100(the molded body 100 a) which is a primary vulcanized molded article, itis preferable to perform secondary vulcanization after the partingoperation process or before the parting operation process.

<Advantages of the Method for Manufacturing the Sealing Device Accordingto the Present Example>

According to the method for manufacturing the sealing device 100according to the present example, by conducting the parting operation onthe cylindrical molded body 100 a, the plurality of sealing devices 100can be obtained from the one molded body 100 a. Accordingly,manufacturing efficiency can be improved in comparison with the casewhere individual sealing devices are molded separately. In addition,upon conducting the parting operation, it can be conducted along thecenter position of each of the cylindrical surface portions 130 in theaxial direction on the outer peripheral side of the molded body 100 a sothat the positioning thereof becomes easy, and the positional accuracyof the parting operation can be improved. Accordingly, even in the caseof the sealing device 100 which requires the annular inner peripheralconvex portions 120 on the inner peripheral side thereof, there is noneed to confirm the positions of the inner peripheral convex portions120, and hence it becomes possible to improve the positional accuracy ofthe parting operation. Note that in the present example, the lengths ofthe cylindrical surface portions 111, 112 in the axial directionprovided on the both sides of the outer peripheral convex portion 110,and the lengths of the cylindrical surface portions 121, 122 in theaxial direction provided on the both sides of the inner peripheralconvex portion 120 are set to be the same. For this reason, the casewhere the parting operation is conducted along the center position inthe axial direction of each of the cylindrical surface portions 130 hasbeen described, but it goes without saying that in cases where theselengths are not set to be the same, the parting operation is conductedat a position offset from the center position.

Second Example

A second example of the present disclosure is shown in FIG. 11. In theabove-mentioned first example, the projection heights of the outerperipheral convex portion and the inner peripheral convex portion of thesealing device are made equal to each other, but in contrast to this, inthe present example, a configuration in which the projection height ofan outer peripheral convex portion of a sealing device is set to behigher than the projection height of an inner peripheral convex portionthereof will be described.

Other configurations and operations are the same as those in theabove-mentioned first example, and hence, the same component parts asthose of the above-mentioned first example are denoted by the samereference signs and the explanations thereof are omitted as appropriate.In addition, a method for manufacturing the sealing device is also thesame as in the case of the above-mentioned first example, so theexplanation thereof is omitted.

FIG. 11 is a schematic cross sectional view showing a fitted state ofthe sealing device according to the second example of the presentdisclosure when fitted in a fitting groove. As mentioned above, in themolding process in the first example, after the material has solidifiedin the molds, the inner mold 521 is moved in a lower direction in FIG. 7together with the lower mold 523, in a state where the molded body 100 ais held inside the outer mold 522. Here, convexes and concaves areformed on the outer periphery of the inner mold 521 and on the innerperiphery of the molded body 100 a, and hence there exists so-calledundercuts. Accordingly, the higher the projection height of the innerperipheral convex portion of the molded body 100 a is set, the largerthe demolding resistance becomes. Note that when the molded body 100 ais taken out from the outer mold 522 after the inner mold 521 has beenmoved, the molded body 100 a can elastically deform to the inner side,so the demolding property of the outer peripheral convex portions do notcause much of a problem. With this reason, it is preferred that theprojection heights of the inner peripheral convex portions of the moldedbody 100 a be made lower in order to improve the demolding property.Note that it goes without saying that the projection heights of theinner peripheral convex portions of the molded body 100 a and theprojection height of the inner peripheral convex portion of the sealingdevice 100 are equal to each other.

Accordingly, in a sealing device 100 according to the present example,the projection height of an inner peripheral convex portion 120X is setto be relatively low, whereas the projection height of an outerperipheral convex portion 110X is set to be relatively high. Morespecifically, the projection height of the inner peripheral convexportion 120X (the projection height from cylindrical surface portions121, 122) is set within a range from 0.1 mm to 0.3 mm, inclusive,whereas the projection height of the outer peripheral convex portion110X (the projection height from cylindrical surface portions 111, 112)is set within a range from 0.4 mm to 0.8 mm, inclusive.

In the case of the sealing device 100 according to the present exampleconfigured as above, the similar operational effects as those in thecase of the sealing device 100 according to the above-mentioned firstexample can be obtained, as well. Note that the sealing device 100according to the present example can be preferably used for usage inwhich it is fitted in a fitting groove 210 of a shaft 200 so as to allowthe outer peripheral convex portion 110X to slide on an inner peripheralsurface of a shaft hole in a housing. In the case of the presentexample, the projection height of the inner peripheral convex portion120X is lower in comparison with that in the first example, and hence,the demolding property is superior than the case of the first example.

In addition, in the case of the present example, the projection heightof the outer peripheral convex portion 110X is set to be relativelyhigh, and hence, it becomes possible to set a distance “a” from a groovebottom surface to the cylindrical surface portions 111, 112 to beshorter than depth “b” of the fitting groove 210, when the sealingdevice 100 is in a state where it is fitted in the fitting groove 210.

As described, by setting the above-mentioned distance “a” to be shorterthan the depth “b”, it is possible to suppress the edge portions of theends of the cylindrical surface portions 111, 112 from interfering withthe corner portions of the fitting groove 210 and thereby being damaged.As a result, there is no need to form relatively large chamfers 211between the side surfaces of the fitting groove 210 and the surface ofthe shaft 200.

Third Example

A third example of the present disclosure is shown in FIG. 12. In theabove-mentioned first example, the projection heights of the outerperipheral convex portion and the inner peripheral convex portion of thesealing device are made equal to each other, but in contrast to this, inthe present example, a configuration in which the projection height ofan inner peripheral convex portion of a sealing device is set to behigher than the projection height of an outer peripheral convex portionthereof will be described.

Other configurations and operations are the same as those in theabove-mentioned first example, and hence, the same component parts asthose of the above-mentioned first example are denoted by the samereference signs and the explanations thereof are omitted as appropriate.In addition, a method for manufacturing the sealing device is also thesame as in the case of the above-mentioned first example except for apoint that a molded body is held not in an outer mold but on an innermold at the time of demolding, and hence, the explanation thereof isomitted as appropriate.

FIG. 12 is a schematic cross sectional view showing a fitted state ofthe sealing device according to the third example of the presentdisclosure when fitted in a fitting groove. In a sealing device 100according to the present example, the projection height of an innerperipheral convex portion 120Xa is set to be relatively high, whereasthe projection height of an outer peripheral convex portion 110Xa is setto be relatively low. More specifically, the projection height of theinner peripheral convex portion 120Xa (the projection height fromcylindrical surface portions 121, 122) is set within a range from 0.4 mmto 0.8 mm, inclusive, and the projection height of the outer peripheralconvex portion 110Xa (the projection height from cylindrical surfaceportions 111, 112) are set within a range from 0.1 mm to 0.3 mm,inclusive.

In a molding process in the present example, when an inner mold 521 ismoved in a lower direction in FIG. 7 together with a lower mold 523,after a material has solidified in the molds, a molded body 100 a isbeing held on the inner mold 521 and hence it is moved in the lowerdirection together with the lower mold 523. Here, convexes and concavesare formed on the inner periphery of the outer mold 522 and on the outerperiphery of the molded body 100 a, and hence there exists so-calledundercuts. However, in the present example, because the projectionheight of the outer peripheral convex portion 110Xa of the sealingdevice 100 is set to be relatively low (the projection heights of theouter peripheral convex portions of the molded body 100 a are set to berelatively low), it is possible to reduce the demolding resistance. Notethat when the molded body 100 a is removed from the inner mold 521, themolded body 100 a can be elastically deformed to an outer side, so thedemolding property of the inner peripheral convex portion does not causemuch of a problem.

In the case of the sealing device 100 according to the present exampleconfigured as above, the same operational effects as in the case of thesealing device 100 according to the above-mentioned first example can beobtained, as well. Note that the sealing device 100 according to thepresent example can be preferably used for usage in which it is fittedin an annular fitting groove 310 formed on an inner periphery of a shafthole 310 in a housing 300 so as to allow the inner peripheral convexportion 120Xa to slide on an outer peripheral surface of a shaft.

In addition, in the case of the present example, too, the projectionheight of the inner peripheral convex portion 120Xa is set to berelatively high, and hence, it becomes possible to set a distance “a”from a groove bottom surface to the cylindrical surface portions 121,122 to be shorter than a depth “b” of the fitting groove 310, when thesealing device 100 is in a state where it is fitted in the fittinggroove 310 as in the case of the second example. Accordingly, the sameoperational effects as in the case of the above-mentioned second examplecan be obtained.

Fourth Example

A fourth example of the present disclosure is shown in FIG. 13. In theabove-mentioned first example, the projection heights of the outerperipheral convex portion and the inner peripheral convex portion of thesealing device are made equal to each other, but in contrast to this, inthe present example, a configuration in which the projection height ofan outer peripheral convex portion of a sealing device is set to behigher than the projection height of an inner peripheral convex portionthereof, and a tip end of the inner peripheral convex portion is formedinto a cylindrical surface.

Other configurations and operations are the same as those in theabove-mentioned first example, and hence, the same component parts asthose of the above-mentioned first example are denoted by the samereference signs, and the explanations thereof are omitted asappropriate. In addition, a method for manufacturing the sealing deviceaccording to the present example is also the same as in the case of theabove-mentioned first example, so the explanation thereof is omitted.

FIG. 13 is a schematic cross sectional view showing a fitted state ofthe sealing device according to the fourth example of the presentdisclosure when fitted in a fitting groove. In a sealing device 100according to the present example, too, the projection height of an innerperipheral convex portion 120Y is set to be relatively low, whereas theprojection height of an outer peripheral convex portion 110Y is set tobe relatively high, as in the case of the above-mentioned secondexample. More specifically, the projection height of the innerperipheral convex portion 120Y (the projection height from cylindricalsurface portions 121, 122) is set within a range from 0.1 mm to 0.3 mm,inclusive, and the projection height of the outer peripheral convexportion 110Y (the projection height from cylindrical surface portions111, 112) is set within a range from 0.4 mm to 0.8 mm, inclusive.

In addition, in the case of the sealing device 100 according to thepresent example, a tip end of the inner peripheral convex portion 120Yis formed into a cylindrical surface.

Accordingly, in the case of the present example, too, it becomespossible to set a distance “a” from a groove bottom surface to thecylindrical surface portions 111, 112 to be shorter than a depth “b” ofa fitting groove 210, when the sealing device 100 is in a state where itis fitted in the fitting groove 210, as in the case of the secondexample.

In the case of the sealing device 100 according to the present exampleconfigured as above, the same operational effects as in the case of thesealing device 100 according to the above-mentioned each example can beobtained, as well.

Moreover, in the case of the sealing device 100 according to the presentexample, the tip end of the inner peripheral convex portion 120Y isformed into the cylindrical surface, and hence, in cases where it isused for usage in which the sealing device 100 is fitted into thefitting groove 210 formed in a shaft 200, the mounting stability thereofcan be improved in comparison with the cases of the above-mentionedfirst through third examples. However, in comparison with the cases ofthe above-mentioned first through third examples, the sealing device 100may become difficult to deform within the fitting groove 210. For thisreason, the sliding property of the outer peripheral convex portion 110Ymay become lower than that in the cases of the first through thirdexamples.

Fifth Example

A fifth example of the present disclosure is shown in FIG. 14. In theabove-mentioned first example, the projection heights of the outerperipheral convex portion and the inner peripheral convex portion of thesealing device are made equal to each other, but in contrast to this, inthe present example, a configuration in which the projection height ofan inner peripheral convex portion of a sealing device is set to behigher than the projection height of an outer peripheral convex portionthereof, and a tip end of the outer peripheral convex portion is formedinto a cylindrical surface.

Other configurations and operations are the same as those in theabove-mentioned first example, and hence, the same component parts asthose of the above-mentioned first example are denoted by the samereference signs and the explanations thereof are omitted as appropriate.In addition, a method for manufacturing the sealing device is also thesame as in the case of the above-mentioned first example except for apoint that a molded body is held not in an outer mold but on an innermold at the time of demolding, and hence, the explanation thereof isomitted.

FIG. 14 is a schematic cross sectional view showing a fitted state ofthe sealing device according to the fifth example of the presentdisclosure when fitted in a fitting groove. In a sealing device 100according to the present example, the projection height of an innerperipheral convex portion 120Ya is set to be relatively high, whereasthe projection height of an outer peripheral convex portion 110Ya is setto be relatively low. More specifically, the projection height of theinner peripheral convex portion 120Ya (the projection height fromcylindrical surface portions 121, 122) is set within a range from 0.4 mmto 0.8 mm, inclusive, and the projection height of the outer peripheralconvex portion 110Ya (the projection height from cylindrical surfaceportions 111, 112) is set within a range from 0.1 mm to 0.3 mm,inclusive. Note that a molding process in the present example is thesame as that in the case of the third example.

In the case of the sealing device 100 according to the present exampleconfigured as above, too, the same operational effects as in the case ofthe sealing device 100 according to the above-mentioned each example canbe obtained.

In addition, in the case of the sealing device 100 according to thepresent example, a tip end of the outer peripheral convex portion 110Yais formed into a cylindrical surface, so that in cases where it is usedfor usage in which the sealing device 100 is fitted into an annularfitting groove 310 formed in an inner periphery of a shaft hole in ahousing 300, the mounting stability thereof can be improved, as in thecase of the above-mentioned fourth example.

(Others)

In the above-mentioned molding process, there has been shown the casewhere injection molding is conducted, but the molded body 100 a may bemolded by other molding methods. For example, the molded body 100 a canalso be molded by compression molding. Note that the compression moldingis a molding method in which a molding material is placed into a cavityin opened molds, then the molds are closed and heated under highpressure for a certain period of time, thereby causing the material inthe molds to solidify, and then the molds are opened and a moldedarticle is taken out therefrom. In addition, the effects of the sealingdevice 100 itself in each example can be obtained even in cases whereeach sealing device 100 is molded individually.

REFERENCE SIGNS LIST

-   100: sealing device-   100 a: molded body-   110, 110X, 110Xa, 110Y, 110Ya: outer peripheral convex portions-   111, 112: cylindrical surface portions-   120, 120X, 120Xa, 120Y, 120Ya: inner peripheral convex portions-   121, 122: cylindrical surface portions-   130: cylindrical surface portion-   140: cylindrical surface portion-   150: material-   200: shaft-   210: fitting groove-   300: housing-   310: shaft hole-   500: screw type injection molding machine-   510: injection mechanism-   520: mold mechanism-   521: inner mold-   522: outer mold-   523: lower mold-   610: rotating mechanism-   620: parting operation tool, C: cavity, S: annular gap

What is claimed is:
 1. A sealing device, that is an elastomeric sealingdevice and is fitted in an annular fitting groove formed on one of twomembers configured to be reciprocally movable relative to each other, soas to seal an annular gap between these two members, wherein: on anouter peripheral side thereof, an annular outer peripheral convexportion; and cylindrical surface portions provided on both sides of theouter peripheral convex portion are formed; and on an inner peripheralside thereof, an annular inner peripheral convex portion; andcylindrical surface portions provided on both sides of the innerperipheral convex portion are formed.
 2. The sealing device as set forthin claim 1, wherein a projection height of the outer peripheral convexportion is equal to a projection height of the inner peripheral convexportion.
 3. The sealing device as set forth in claim 2, wherein theprojection height of the outer peripheral convex portion and theprojection height of the inner peripheral convex portion are set withina range from 0.2 mm to 0.4 mm, inclusive.
 4. The sealing device as setforth in claim 1, wherein a projection height of the outer peripheralconvex portion is higher than a projection height of the innerperipheral convex portion.
 5. The sealing device as set forth in claim4, wherein the projection height of the outer peripheral convex portionis set within a range from 0.4 mm to 0.8 mm, inclusive, and theprojection height of the inner peripheral convex portion is set within arange from 0.1 mm to 0.3 mm, inclusive.
 6. A molded body formanufacturing a sealing device, wherein: the molded body is formed intoa cylindrical shape; the molded body is provided with a plurality ofcylindrical surface portions and a plurality of annular outer peripheralconvex portions arranged alternately on an outer peripheral sidethereof, and provided with a plurality of cylindrical surface portionsand a plurality of annular inner peripheral convex portions arrangedalternately on an inner peripheral side thereof; the cylindrical surfaceportions at the outer peripheral side and the cylindrical surfaceportions at the inner peripheral side are provided so as to be at thesame positions in an axial direction; and the outer peripheral convexportions and the inner peripheral convex portions are also provided soas to be at the same positions in the axial direction.
 7. The moldedbody as set forth in claim 6, wherein projection heights of the outerperipheral convex portions are higher than projection heights of theinner peripheral convex portions.